Wireline logging operations are performed in a well to measure one or more physical properties of the formation with respect to depth and/or time in or around a wellbore. Such operations are typically performed by connecting a string of logging tools to a wireline cable and lowering the logging tools into a well adjacent to an area of interest within the well. Once within the area of interest, the logging tools are used to make measurements of the physical properties of the formation of interest, as well as wellbore parameters, and to transmit data indicative of the measured properties to the surface of the well through the wireline cable.
Such data transmission is commonly performed by sending electrical signals through electrical lines from the logging tool to the wireline cable, and up the wireline cable to the data acquisition equipment at the well surface. Power transmission to the logging tool is similarly commonly performed by use of electrical lines connecting the logging tool and the wireline cable. However, during such operations, depending on the downhole environment, such electrical data and power transmission can encounter several problems. For example, electrical data transmission lines often experience electromagnetic interference from nearby high voltage conductors, motors, cables, or other electromagnetic devices; electrical data transmission occurs at a relatively slow speed; electrical lines are relatively expensive to maintain; and electronic signals often need to be amplified and/or strengthened in order to be transmitted effectively.
Also, some downhole logging tools gather enormous volumes of data which need to be transmitted uphole at faster rates for real time high speed data and image processing than can be accomplished by transmission across electrical lines. In such situations, the logging tool's logging speed has to be reduced in order to compensate for the relatively slow data transmission across the electrical lines and to prevent data overload. This results in undesirable delay in the overall job completion.
Accordingly, a need exists for a method and a device for improving the speed of data transmission in a wireline logging operation.